From the past, considerable efforts have been directed to the reduction of the size and the weight of automotive equipment using electric motors. This is particularly important because, in recent years, an increasing number of motor driven accessories have come to be used in each automobile to the end of improving the performance and the convenience of the automobile. Manual operations required for achieving the actions of various moving parts of the automobile equipment have been taken over by electric motors to a large extent. For instance, a typical high grade automobile is equipped with a motor driven side window system, a windshield wiper system, a motor-driven sun roof, a power seat adjustment system and so on.
As a result, each automobile is equipped with so many electric motors that there is now a shortage of space for accommodating the control devices for these motors. Typically, control devices for on-board electric motors are built as individual units and fitted into spaces defined behind instrument panels, under the seats and so on. And, each electric motor requires a manual control switch and a control device and they must be connected by electric wires in the form of a wire harness. Therefore, not only the arrangement of the control devices and the electric motors but also the arrangement of the electric wires connecting the manual switches, the control devices and the motors tend to place a severe burden in designing and manufacturing on-board motor systems. Also, the complication of the control devices and electric wires causes a great difficulty in servicing the motor-driven automotive equipment.
Thus, it is desired to simplify the arrangement of the motor-driven automotive equipment but the reliability of the operation of the equipment must be assured at the same time. This is particularly important because automotive equipment is placed under severe operating conditions because it is often exposed to extreme temperatures and severe vibrations.